the first and second basibranchials, and dorsally with the 

 second ceratobranchial. Second ceratobranchial only 

 slightly shorter than the first ceratobranchial; slightly 

 expanded anteroventrally; articulates dorsally with the 

 second epibranchial. Second epibranchial a short rod; ar- 

 ticulates dorsally with the posterolateral surface of the 

 second pharyngobranchial. Second pharyngobranchial 

 the first and larger of the two toothed pharyngo- 

 branchial elements; even in the largest specimen studied 

 (350 mm) it remains partially unossified, because a large 

 cartilaginous region is present anterodorsally in its mass; 

 more or less squarish in outline, except for its concave 

 and vertically oriented posterior surface; articulates 

 along its lateral surface posteriorly with the second epi- 

 branchial and anteriorly with the first epibranchial; ar- 

 ticulates along its concave posterior surface by fibrous 

 tissue to the rounded anterior surface of the third 

 pharyngobranchial. The posterior surface of the second 

 pharyngobranchial is more deeply concave ventrally 

 than dorsally, so that the ventral surface of the element 

 is U-shaped. It bears an irregular band of up to about 25 

 minute teeth on its ventral surface along the bend of the 

 U. The teeth are so small that it is doubtful if they are 

 functional or even if they protrude to the surface through 

 the skin of the oral cavity. 



Third arch. — Basi-, hypo-, cerato-, epi-, and 

 pharyngobranchial elements present. Third basi- 

 branchial the widest of the basibranchial elements; rec- 

 tangular in shape; articulates anteriorly with the second 

 basibranchial, anterolaterally with the second hypo- 

 branchials, posterolaterally with the third hypo- 

 branchials and third ceratobrtmchials, and posteriorly 

 with the fourth ceratobranchials. Third hypobranchial a 

 relatively straight and slender rod; articulates postero- 

 laterally with the third ceratobranchial and postero- 

 medially with the third basibranchial, while its ven- 

 trally directed anterior end articulates by fibrous tissue 

 with the under surface of the more anterior basi- 

 branchial elements. Third ceratobranchial articulated 

 ventrally with the posterior ends of the third hypo- 

 branchial and third basibranchial, and dorsally with the 

 third epibranchial. Third epibranchial rodlike; slightly 

 expanded anteriorly in the middle of its length, at which 

 place it makes fibrous tissue contact with the posterior 

 surface of the second epibranchial; articulates dorsally 

 with the lateral surface of the third pharyngobranchial. 

 Third pharyngobranchial smaller than the second 

 pharyngobranchial; more or less columnar; its ventral 

 surface concave; better ossifed than the second pharyn- 

 gobranchial, but nevertheless with several cartilaginous 

 areas present; articulates anteriorly with the concave 

 posterior surface of the second pharyngobranchial and 

 laterally with the dorsal ends of the third and fourth epi- 

 branchials. It usually bears one to six minute and non- 

 protruding teeth in a row along the anterior edge of its 

 ventral surface, but no such even rudimentary teeth 

 could be found in some of the specimens examined. 



Fourth arch. — Cerato- and epibranchial elements 



only. Fourth ceratobranchial much expanded ventrally; 

 articulates ventrally with the posterior end of the third 

 basibranchial and dorsally with the fourth epibranchial. 

 Fourth epibranchial the longest of the epibranchial 

 elements; much wider ventrally than dorsally; ar- 

 ticulates dorsally with the lateral surface of the third 

 pharyngobranchial. 



Fifth arch. — Ceratobranchial (lower pharyngeal) 

 element only. Fifth ceratobranchial the shortest of the 

 ceratobranchial elements; much expanded ventrally 

 throughout the middle region of its length; articulates 

 ventrally with the ventral end of the fourth cerato- 

 branchial; toothless. 



PAIRED FIN GIRDLES. 



Pectoral Fin. 



Posttemporal. — A large long shaft broadly over- 

 lying the lower half of the lateral surface of the pterotic, 

 to which it is firmly interdigitated; anterodorsally it also 

 interdigitates, to a much lesser extent, with the 

 sphenotic, while its ventral head is firmly held by fi- 

 brous tissue to the supracleithrum. On its ventromedial 

 surface the posttemporal helps, along with the pterotic 

 and, to a far lesser extent, the cleithrum, to support by fi- 

 brous tissue the expanded lateral end of the ossified 

 Baudelot's ligament. 



Baudelot's ligament. — The ligament fully ossified 

 as a large stout shelf giving great support to the pectoral 

 girdle. It articulates firmly by fibrous tissue at its medial 

 end with the extreme posterolateral edge of the pttra- 

 sphenoid immediately anterior to the posteriormost 

 point of contact between the parasphenoid and basioc- 

 cipital. Its expanded lateral end is firmly held by fibrous 

 tissue mainly to the ventromedial surface of the ventral 

 flange of the pterotic and to the ventral end of the post- 

 temporal, and, to a much lesser extent, to the extreme 

 dorsolateral end of the cleithrum. The dorsal edge of the 

 medially expanded platelike portion of the cleithrum is 

 firmly held by a sheet of fibrous tissue to the ventral sur- 

 face of Baudelot's ligament. 



Supracleithrum. — Located slightly obliquely pos- 

 terodorsally to anteroventrally in relation to the axis of 

 the body; relatively short and broadly overlain by the 

 posttemporal; articulates firmly by fibrous tissue, and 

 slight interdigitation in large specimens, dorsally with 

 the overlying posttemporal and ventrally with the cleith- 

 rum, which it broadly overlies. 



Cleithrum. —Greatly expanded both laterally and 

 medially along all the length of its anterior edge, except 

 for a short distance ventrally, so that a large thin ver- 

 tical plate is formed at right angles to the axis of the 

 body; also greatly expanded posteriorly in the ventral 

 half of its length; articulates dorsally by fibrous tissue 



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